Effects of aryl substituents on the performance of polysilsesquioxane-based CO2 separation membranes

Reducing CO 2 emissions is of primary importance in addressing global warming. Membrane separation of CO 2 has been actively studied as a straightforward and low-cost CO 2 separation method. In this study, new polysilsesquioxane (PSQ)-based membranes were prepared by the 1:1 copolymerization of (triethoxysilylethyl)benzene (TESEB), (triethoxysilylethyl)pyridine (TESEPy), and (triethoxysilylethyl)naphthalene (TESENp) with bis(triethoxysilyl)ethane (BTESE), and their CO 2 separation performance was evaluated. Among them, the TESEB-BTESE membrane exhibited the highest CO 2 /N 2 permselectivity of 49.6 with a CO 2 permeance of 2.03 × 10 −7 mol m −2 s −1 Pa −1 (606 GPU). The CO 2 permeance of the TESEPy-BTESE membrane increased from 1.47 × 10 −7 (439 GPU) to 3.34 × 10 −7 mol m −2 s −1 Pa −1 (997 GPU) after the membrane was stored at 200 °C for 4 weeks in a nitrogen atmosphere, although CO 2 /N 2 permselectivity slightly decreased from 20.0 to 16.5. DFT calculations were performed to understand the effects of aryl substituents on the CO 2 separation performance, providing important information for the molecular design of PSQ-based membranes for CO 2 separation.